Radio communication devices include a transmitter and/or a receiver coupled to an antenna which emits and/or detects radio frequency signals. The device may include a microphone for inputting audio signals to a transmitter or a speaker for outputting signals received by a receiver. Examples of such radio communication devices include one-way radios, two-way radios, radio telephones, personal communication devices, and a variety of other equipment. These communication devices often have a standby configuration wherein the device is collapsed for storage and an active communication configuration, wherein the antenna is extended for optimum performance.
For radio telephones and two-way radios, it is typically desirable that these devices have a small size during a standby mode to facilitate storage and transport thereof. For example, users prefer that the radio telephones are small enough in the standby mode to permit storage in a shirt or jacket pocket. In the active communication state, it is desirable for the device to be sufficiently long to position the speaker adjacent to the user's ear, the microphone near the user's mouth, and the antenna away from the user's body. It is desirable for the antenna to be positioned away from the user's body since the user's body is a large conductor that interferes with radio frequency signal reception. One particularly effective way of positioning the antenna away from the user's body is to extend the antenna away from the device body during use. By providing an antenna which collapses for storage and extends for optimum performance during an active communication mode, the antenna's high performance active mode operation is provided in a readily storable device.
A difficulty encountered with such reconfigurable communication devices is providing a high performance antenna in the standby mode. The body of the device, including internal electronic circuitry within the body, is typically in the reactive near-field of the antenna in the storage position. This object in the reactive near-field of the antenna can degrade standby performance of devices, such as radio telephones, which receive paging signals, electronic mail, or call alerting signals in the standby mode.
Accordingly, it is desirable to provide an antenna having high performance characteristics when the communication device is extended in an active communication mode and when the communication device is collapsed in a standby mode of operation.